TWI523255B - Method for manufacturing light-emitting device on substrate - Google Patents

Description

Method for manufacturing light-emitting device on substrate

The present disclosure relates to a method of manufacturing a package having a light-emitting device on a substrate.

The design of a package for storing light-emitting diodes (LEDs) or other light-emitting devices is an important factor in optimizing the amount of light output from the package. LEDs are often stored in packages containing multiple components that occupy a much larger area than the LED chips themselves. In order to increase the amount of light emitted from the package, reflective materials such as metallization are sometimes provided on the inner surface of the package. In order to maximize the amount of light reflected from the package, it is preferred to provide a reflective material on a significant portion of the interior of the package.

In some packages, the LED wafer is bonded to a thermally conductive gasket. The metallization of the reflective mirror can also be used as a thin film stack of partially conductive pads and plated through wafer interconnects. However, these processes tend to complicate the process and reduce the amount of package surface that can be used to reflect light from the package.

In one aspect, a method of fabricating a package having a light emitting device such as an LED includes depositing a first metallization to form a conductive pad on which the light emitting device will be mounted, and forming an extension through the support of the conductive pad One or more feed-through interconnections of semiconductor material. Subsequently, a second metallization is deposited to form a reflective surface for reflecting the light emitted by the illumination device through the cover over the package. The deposition of the second metallization is de-coupled from the deposition of the first metallization, which in some cases may increase the coverage of the reflective metallization The area, thereby increasing the amount of light reflected from the package.

In some embodiments, the first metallization is deposited to form respective overhangs around the top of each of the conductive shim and the feedthrough interconnects. The second metallization is deposited on the surface of the semiconductor material such that the overhangs act as a shield to substantially prevent the second metallization from being deposited on regions directly below the overhangs. This technique allows the second metallization to form a reflective surface that is electrically interrupted by the conductive pads and the feedthrough interconnects.

Some embodiments include forming a cavity on a first side of the semiconductor wafer and forming one or more vias extending from a bottom of the cavity to a second side of the wafer. The first metallization is deposited to form the conductive pad for mounting the light emitting device and form a feedthrough interconnect extending through the one or more vias. The first metallization is deposited to form overhangs around the top of each of the conductive pads and the feedthrough interconnects. The second metallization is deposited on the first side of the semiconductor wafer, on the bottom and side surfaces of the cavity, and on the conductive pad and the upper surface of the feedthrough interconnect. The overhangs serve as a shield to substantially prevent the second metallization from being deposited on the area directly under the overhangs. Selectively removing the second metallization from the conductive pads and upper surfaces of the feedthrough interconnects such that the remaining second metallization is electrically interconnected with the conductive pads and the feedthroughs Interrupted reflective surface. The illuminating device is then mounted on the conductive shim.

The details of one or more embodiments of the invention are set forth in the drawings Other features and advantages of the invention will be set forth in the description and appended claims.

As illustrated in the example of FIG. 1, the two structures 12, 14 are soldered together to provide a hermetic package 10 enclosing a light emitting device such as LED 16. Techniques other than soldering (such as, but not limited to, anodic bonding and adhesive bonding) can also be used. The upper structure 12 acts as an upper cover and can be penetrated by the wavelength emitted by the LEDs 16.

In the illustrated example, LED wafer 16 is mounted on conductive spacers 18 on lower structure 14 as a substrate. A welded seal ring 20 is provided on the cavity side surface of the base structure 14 for sealingly attaching the upper cover 12 to the base.

Figure 2 is a top view of the substrate 14 with the LED wafer 16 removed.

As shown in FIGS. 1 and 2, the LED 16 is mounted in a cavity 22 formed in a substrate 14, which also includes a feedthrough metallization 24. Other circuits and passive components can be mounted in the cavity 22 and enclosed within the package. The feedthrough metallization 24 extends through one or more microvias (i.e., vias) in the lower portion of the substrate 14. As depicted in the example of FIG. 1, feedthrough metallization 24 extends along the outer surface of substrate 14 and can be electrically connected to solder bumps 26 of the printed circuit board assembly. Wire bond 28 can provide an electrical connection from LED wafer 16 to feedthrough metallization 24. Alternatively, the LED 16 can be directly flip-chip bonded to the feedthrough metallization 24. Metallization 30 is also disposed on the inner surface of substrate 14, including bottom 32 and side walls 34, and serves as a mirror for reflecting additional light from LEDs 16 through upper cover 12.

For example, the substrate 14 can be formed from a germanium wafer and the vias 22 and the vias of the feedthrough metallization 24 are etched therein using standard techniques. For example, a double sided etching technique can be used.

The metallization of the spacer 18 and the feedthrough connection 24 is then deposited, as well as the mirror metallization 30. As will be explained in more detail below, the deposition of mirror metallization 30 is separated from the deposition of metallization of spacers 18 and feedthrough connections 24.

Figures 3 through 7 depict the manufacturing steps for depositing various metallized layers. As shown in FIG. 3, after etching the recess 22 and the via of the feedthrough metal 24, and depositing or growing a passivation layer, a thin film metallization stack 40 is deposited on the surface of the wafer, contained in the cavity and In these through holes. In the illustrated example, film stack 40 comprises a layer of aluminum (Al), titanium (Ti), nickel (Ni), and gold (Au). Other embodiments may include less than all of the foregoing materials. Furthermore, additional or different materials may be included for the film stack in other embodiments.

Next, the thin plated mold 42 is placed on the surface of the tantalum wafer except for the region where the feedthrough metallization 24 and the conductive spacer 18 are to be deposited. A photoresist mask can be used as the plating mold 42. Although Figures 3-7 depict an example of feedthrough metallization 24, the same treatment is applied to the gasket metallization 18. For example, the photoresist mask can be deposited by any of several techniques including spin coating, dip coating, spray coating, or electrodeposition.

After depositing the plating mold 42, for example, a plating process is used to deposit the metallization of the feedthrough connection 24 and the spacer 18. The plated metallization 18, 24 is deposited such that there are overhangs around the top of each conductor wire and/or pad. An enlarged example of this overhanging portion 100 is depicted in Fig. 8. During subsequent processing, the overhang 100 is used as a shield to prevent the mirror metallization 30 from being deposited too close to the metallized side edges of the feedthrough connection 24 and the spacer 18.

In the example, gold (Au) or gold-tin is used as the metallization of the feedthrough connection 24 and the spacer 18. Once the thickness of the deposited gold exceeds the thickness of the plating mold 42, the isotropic growth of the gold layer results in the formation of the overhang 100. In the illustrated example, the thickness of the plating mold 42 is about 7 to 8 micrometers (μm), and the thickness of the gold metal plating is about 10 μm. The thickness of the overhangs is about 2 to 3 μm. Similarly, in the illustrated example, the overhang 100 extends beyond the lower portion of the metallization by about 2 to 3 μm. In other implementations These values can be different.

Next, as described in FIG. 4, the plating mold 42 is removed and the remaining film stack 40 is patterned to form a metal structure, such as a solder bond 44 and a solder dam, on the back side of the germanium wafer ( Solder dam)46. In the illustrated example, the weld 44 includes all of the layers of the film stack 40; the weld dam 46 includes the Al and Ti layers.

Next, as shown in Fig. 5, a mirror-plated metal (e.g., aluminum) 30 is deposited substantially on all exposed areas on the cavity side of the substrate 14. The mirror metallization 30 can be deposited using evaporation or sputtering techniques, the final thickness of which should be less than the thickness of the feedthrough connection 24 and the metallized lower portion of the conductive spacer 18. In the illustrated example, the mirror metallization 30 has a thickness of about one hundred nanometers (nm). As described in FIG. 5, the mirror metallization is deposited on the top of the overhang 100 and the exposed area on the cavity side of the substrate 14. However, as described above, and as more clearly depicted in FIG. 9, the feedthrough connection 24 and the overhang 100 of the conductive shim 18 serve as a shield and prevent the specular metallization from being deposited too close to the feedthrough connection 24. And the edge of the spacer 18.

As explained in the previous description, the process of depositing the mirror metallization 30 is separate from the process of depositing the metallization of the feedthrough connection 24 and the conductive shim 18. This may result in the mirror metallization covering the inner surface of most of the substrate 14 while preventing the mirror metallization 30 from contacting the side edges of the feedthrough connection 24 and the spacer 18.

Next, as shown in FIG. 6, the aluminum mirror metallization 30 is removed from the gold plated layers 24, 18 (i.e., the aluminum is removed from the top of the feedthrough connection 24 and the conductive spacer 18). For example, it can be achieved by selectively depositing a photoresist layer 48 (eg, by electrodeposition techniques) on the area of the aluminum mirror metallization layer 30, without depositing on those aluminum mirror metallization layers. The removed area (i.e., not deposited on the feedthrough connection 24 and the conductive shim 18). The gold (or gold) can then be removed by placing the germanium wafer in an aluminum etchant. - Tin) Feedthrough connection 24 and exposed aluminum plated metal on top of conductive spacer 18.

After the aluminum is removed from the feedthrough connection 24 and the conductive spacer 18, the electrodeposited photoresist layer 48 is stripped as shown in FIG. As a result, a significant portion of the inner surface of the semiconductor substrate for the LED wafer is covered by a reflective (mirror) metallization to enhance the optical output. Due to the overhang 100, the mirror metallization is electrically interrupted from the conductor lines (i.e., the feedthrough connection 24 and the conductive spacer 18).

While the previous description has focused on forming a single package of substrate 14, this process can be performed as batch processing at the wafer level.

After depositing a plurality of metallization layers, the LED wafer 16 is placed on the conductive pads 18 and the bond wires 28 are attached. The cavity 22 can be filled with a polyoxygel and a transparent top cover 12, which can include a plastic or glass lens, can be attached to the substrate 14.

Other embodiments are included in the scope of the patent application.

10‧‧‧Package

12‧‧‧Upper cover

14‧‧‧Base

16‧‧‧LED

18‧‧‧ Conductive gasket

20‧‧‧welding seal ring

22‧‧‧ cavity

24‧‧•Feed through metallization (feedthrough connection)

26‧‧‧ solder bumps

28‧‧‧welding line

30‧‧‧metal plating

32‧‧‧ bottom

34‧‧‧ side wall

40‧‧‧ Film stacking

42‧‧‧ plating

44‧‧‧welding

46‧‧‧ soldering dam

48‧‧‧ photoresist layer

100‧‧‧Overhanging

Fig. 1 is a cross-sectional view showing an example of a package accommodating a light-emitting device.

Figure 2 is a top view of the substrate of the package.

Figures 3 through 7 depict fabrication steps for depositing various metallized layers.

Figure 8 is an enlarged view of the overhang at the top of the metallization of the feedthrough and conduction pads.

Figure 9 depicts how the overhangs shield the area adjacent the side edges of the feedthrough and conductive pad metallization regions from being overlaid by subsequent metallization.

10‧‧‧Package

12‧‧‧Upper cover

14‧‧‧Base

16‧‧‧LED

18‧‧‧ Conductive gasket

20‧‧‧welding seal ring

22‧‧‧ cavity

24‧‧•Feed through metallization (feedthrough connection)

26‧‧‧ solder bumps

28‧‧‧welding line

30‧‧‧metal plating

32‧‧‧ bottom

34‧‧‧ side wall

Claims (28)

A method of fabricating a package having a light-emitting device on a substrate, the method comprising: depositing a first metallization to form a conductive pad on which the light-emitting device is to be mounted, and forming a semiconductor extending through the conductive pad One or more feed-through interconnections of material; and subsequently depositing a second metallization to form a reflective surface for reflecting light emitted by the illumination device through the cover of the package, wherein a first metallization is deposited to form respective overhangs around the top of each of the conductive shim and the one or more feedthrough interconnects, and the second plating is deposited by the overhangs The metal is de-coupled to deposit the first metallization. The manufacturing method of claim 1, further comprising: depositing the second metal plating on a surface of the semiconductor material, including on the conductive pad and the upper surface of the one or more feedthrough interconnections, wherein And the overhangs serve as a shield to substantially prevent the second metallization from being deposited on a region directly under the overhang; and subsequently interconnected from the conductive shim and the one or more feedthroughs The upper surface removes the second metallization. The manufacturing method of claim 2, further comprising depositing the second metal plating substantially on the entire side of the semiconductor material. The manufacturing method of claim 2, wherein the overhanging portions are formed by isotropic growth of the first metal plating. The manufacturing method of claim 4, further comprising: providing a mask layer on the surface of the semiconductor material, the mask layer defining Depositing the conductive pad and the first metallized opening of the one or more feedthrough interconnects; and subsequently depositing the first metallization, wherein the isotropic growth of the first metallization occurs When the thickness of the first metal plating exceeds the thickness of the mask layer. The manufacturing method of claim 5, wherein the mask layer comprises a photoresist. The manufacturing method of claim 6, wherein the photoresist is deposited by spin coating. The manufacturing method of claim 6, wherein the photoresist is deposited by dip coating. The manufacturing method of claim 6, wherein the photoresist is deposited by spraying. The manufacturing method of claim 6, wherein the photoresist is deposited by electrodeposition. The manufacturing method of claim 2, wherein the first metal plating is deposited by a plating process, and the second metal plating is deposited by an evaporation technique. The manufacturing method of claim 2, wherein the first metal plating is deposited by a plating process, and the second metal plating is deposited by a sputtering technique. The manufacturing method of claim 2, wherein the overhangs extend beyond the conductive pads and the respective lower portions of the one or more feedthrough interconnects on a scale of a few microns. The manufacturing method of claim 2, wherein the removing the second metal plating from the conductive pad and the upper surface of the one or more feedthrough interconnects comprises: selectively providing the photoresist layer in addition to The second metallized area outside the second metallized area to be removed; The exposed area of the second metallization is etched. The manufacturing method of claim 2, wherein the first metal plating comprises gold and the second metal plating comprises aluminum. The manufacturing method of claim 2, wherein the first metal plating comprises gold and tin, and the second metal plating comprises aluminum. The manufacturing method of claim 2, further comprising etching a cavity in the semiconductor material, wherein the conductive pad and the one or more feedthrough interconnections are formed in an area defined by the cavity And wherein the second metallization is deposited on a bottom surface of the cavity and along a sidewall of the cavity. The manufacturing method as in the second application of the patent scope is performed as a batch processing at the semiconductor wafer level. A method of fabricating a package for housing a light emitting device, the method comprising: forming a cavity on a first side of a semiconductor wafer and forming one from a bottom of the cavity to a second side of the wafer or a plurality of vias; depositing a first metallization to form a conductive pad for mounting the light emitting device and forming a feedthrough interconnect extending through the one or more vias, wherein depositing the first metallization Forming respective overhangs around the top of each of the conductive pad and the feedthrough interconnects; depositing a second metallization on the first side of the semiconductor wafer, included in the cavity On the bottom and side surfaces, and on the upper surface of the conductive pad and the feedthrough interconnects, wherein the overhangs serve as a shield to substantially prevent the second metallization from being deposited on the overhangs Selecting the second metallization from the conductive gasket and the upper surface of the feedthrough interconnect such that the remaining second metallization is formed with the conductive spacer and the portion Wait The feedthrough interconnects an electrically interrupted reflective surface; and mounting the illumination device on the conductive spacer. The manufacturing method of claim 19, wherein the overhanging portions are formed by isotropic growth of the first metal plating. The manufacturing method of claim 20, further comprising: providing a mask layer on the first side of the semiconductor material, the mask layer defining the conductive pad to be deposited and the feedthrough interconnect a first metallized opening; and subsequently depositing the first metallization, wherein the isotropic growth of the first metallization occurs when the thickness of the first metallization exceeds the thickness of the mask layer. The manufacturing method of claim 19, wherein the first metal plating is deposited by a plating process, and the second metal plating is deposited by an evaporation technique. The manufacturing method of claim 19, wherein the first metal plating is deposited by a plating process, and the second metal plating is deposited by a sputtering technique. The manufacturing method of claim 19, wherein the overhangs extend beyond the conductive pads and the respective lower portions of the feedthrough interconnects on a scale of a few microns. The manufacturing method of claim 19, wherein the first metal plating comprises gold and the second metal plating comprises aluminum. The manufacturing method of claim 19, wherein the first metal plating comprises gold and tin, and the second metal plating comprises aluminum. The manufacturing method of claim 19, further comprising mounting a light emitting diode on the conductive spacer. The manufacturing method of claim 27, further comprising electrically coupling the light emitting diode to the feedthrough interconnects, and attaching a transparent upper cover to the light emitting diode on.